1. Field of the Invention
The present invention relates to a scanning arrangement and method for determining the shape, size or other three-dimensional surface characteristics of an object, such as colour for example.
2. Description of the Related Art
A number of patents and published patent applications disclose optical scanning systems which rely on a scanned laser beam or the like for determining the shape of an object. Usually such systems utilise a fixed mounting for the scanning system and utilise optical triangulation for determining depth information. Examples of such systems include U.S. Pat. No. 4,627,734 (Rex), EP-B-233,920 (Addleman) and WO 94/15173 (Crampton).
There is a need for a scanner for determining shape or other surface characteristics which can be hand-held. As far as we are aware, only one such system is known, namely that disclosed in U.S. Pat. No. 5,198,877 (Schulz) and its equivalent EP-A-553,.266.
The Schulz system requires an externally generated coordinate system defined by an array of photodetectors which detects an array of pilot lights on the scanner. Hence the scanner can only be used within this coordinate system and furthermore the array of pilot lights must be kept in view by the array of photodetectors, which further restricts the mobility of the scanner. This is a serious disadvantage because it is normally necessary to scan the object of interest from all sides in order to build up a complete picture of its surface.